Tornadoes · United States · Illinois · 1965

F1 tornado, Lake County, Illinois, April 11, 1965

This F1 tornado ran 0.5 miles across Lake County on April 11, 1965, touching down at 4:04 PM GMT-6 and reaching 250 yards wide. It killed nobody, and did $50,000 to $500,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. F040 to 72 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. F173 to 112 mphthis tornado

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. F2113 to 157 mph

    Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

  4. F3158 to 206 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. F4207 to 260 mph

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. F5261 to 318 mph

    Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

  7. Unrated

    The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

The record

Rating
F1
Date
April 11, 1965
Touchdown
4:04 PM GMT-6 (22:04 UTC)
Path length
0.5 miles (0.8 km)
Path width
250 yards (229 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Lake County
Touchdown point
42.430, -87.830
Record number
141

The air that afternoon

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Green Bay/Straub, WI (KGRB), 12:00Z

10.1 hours before the tornado, 229 km from the path. April 11, 1965.

Skew-T log-pSkew-T log-p diagram, Green Bay/Straub, WI at 12:00Z on 1965-04-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -16720, lifted condensation level 849 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Green Bay/Straub, WI at 12:00Z on 1965-04-11The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 153 square meters per square second, 0 to 6 km bulk shear 81 knots.1939587897117136Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-16720 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
849 m above ground
0-6 km bulk shear
81 kt
0-1 km bulk shear
17 kt
0-1 km storm-relative helicity
153 m²/s²
0-3 km storm-relative helicity
213 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
3.1 K/km

Open this sounding in Storm Lab

Green Bay/Straub, WI (KGRB), 00:00Z

1.9 hours after it, 229 km from the path. April 12, 1965.

Skew-T log-pSkew-T log-p diagram, Green Bay/Straub, WI at 00:00Z on 1965-04-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 62 joules per kilogram, CIN -55, lifted condensation level 563 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Green Bay/Straub, WI at 00:00Z on 1965-04-12The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 282 square meters per square second, 0 to 6 km bulk shear 37 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
62 J/kg
Mixed-layer CIN
-55 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
563 m above ground
0-6 km bulk shear
37 kt
0-1 km bulk shear
24 kt
0-1 km storm-relative helicity
282 m²/s²
0-3 km storm-relative helicity
423 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5
0-3 km lapse rate
3.3 K/km

Open this sounding in Storm Lab

This ground now

The live radar over the trackEvery 1965 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of April 11, 1965

44 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 113:30 AM GMT-6F2Muskogee, OK0.110$500 to $5,000
April 1112:55 PM GMT-6F4Cedar, IA91.520013$500,000 to $5 million
April 111:15 PM GMT-6F1Chickasaw, IA49.9300$50,000 to $500,000
April 112:00 PM GMT-6F1Green, WI27.116740$500,000 to $5 million
April 112:30 PM GMT-6F2Jefferson, WI14.51,320328$500,000 to $5 million
April 112:45 PM GMT-6F1Crawford, WI13.310$5,000 to $50,000
April 113:20 PM GMT-6F4Crystal Lake tornado, IL9.1400675
April 113:50 PM GMT-6F2Lake, IL4.5200$50,000 to $500,000
April 113:50 PM GMT-6F1Walworth, WI1.950$50,000 to $500,000
April 113:55 PM GMT-6F1Walworth, WI1.010$5,000 to $50,000
April 114:00 PM GMT-6F1Kane, IL0.3150$50,000 to $500,000
April 114:14 PM GMT-6F1Monroe, WI2.050$5,000 to $50,000
April 114:45 PM GMT-6F3Starke, IN35.62501082$5 million to $50 million
April 115:54 PM GMT-5F4Ottawa, MI20.63005142$500,000 to $5 million
April 115:10 PM GMT-6F3Porter, IN33.110$5 million to $50 million
April 116:15 PM GMT-5F4Dunlap tornado, IN21.21031252
April 116:40 PM GMT-5F4Midway tornado, IN21.6177541$50,000 to $500,000
April 116:00 PM GMT-6F4Hillsdale tornado, Indiana and Michigan90.31,76023294$50 million to $500 million
April 117:05 PM GMT-5F1Allegan, MI19.520019$50,000 to $500,000
April 117:07 PM GMT-5F4Tippecanoe, IN21.850044
April 117:10 PM GMT-5F4Twin Lakes tornado, IN37.033336321
April 117:20 PM GMT-5F4Russiaville–Kokomo–Marion tornado, IN48.088025835$50 million to $500 million
April 117:30 PM GMT-5F3Kalamazoo, MI14.215017$50,000 to $500,000
April 117:40 PM GMT-5F3Barry, MI14.1105$50,000 to $500,000
April 117:40 PM GMT-5F4Branch, MI80.51021293
April 117:50 PM GMT-5F4Lebanon–Sheridan tornado, IN45.71,66728123$5 million to $50 million
April 117:10 PM GMT-6F4Berne tornado, Indiana and Ohio52.5104125$5 million to $50 million
April 118:15 PM GMT-5F4Clinton, MI21.010018$50,000 to $500,000
April 118:25 PM GMT-5F2Montcalm, MI15.14401$50,000 to $500,000
April 118:30 PM GMT-5F2Gratiot, MI0.150$5,000 to $50,000
April 118:30 PM GMT-5F2Gratiot, MI0.550$5,000 to $50,000
April 118:30 PM GMT-5F2Gratiot, MI1.050$5,000 to $50,000
April 118:50 PM GMT-5F2Bay, MI9.9102$50,000 to $500,000
April 119:00 PM GMT-5F2Tuscola, MI9.010$50,000 to $500,000
April 118:30 PM GMT-6F4Toledo tornado, Ohio and Michigan5.620018236$5 million to $50 million
April 119:30 PM GMT-5F4Cairo tornado, OH32.540013104$500,000 to $5 million
April 1110:00 PM GMT-5F4Fort Loramie tornado, OH18.4300350$500,000 to $5 million
April 1110:15 PM GMT-5F3Seneca, OH15.0300430$50,000 to $500,000
April 1111:05 PM GMT-5F4Grafton–Strongsville tornado, OH22.040018200$5 million to $50 million
April 1111:15 PM GMT-5F1Preble, OH0.110$5,000 to $50,000
April 1111:30 PM GMT-5F1Medina, OH8.22006$50,000 to $500,000
April 1111:30 PM GMT-5F2Union, OH22.2400462$500,000 to $5 million
April 1111:50 PM GMT-5F1Greene, OH0.110$5,000 to $50,000
April 1112:30 AM GMT-5F1Pickaway, OH38.430013$50,000 to $500,000

What this means

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.